1. Field of the Invention
The present invention relates to a movement detection device, and more specifically, to a device which detects movement vectors from image signals.
2. Related Background Art
One method to detect movement vectors by image signal processing is the time-space gradient method which is described in the Japanese Patent Publication No. 60-46878, in J. O. Limb and J.A. Murply, "Measuring the Speed of Moving Objects from Television Signals", IEEE Trans. Com./ Com-23, 4, pp. 474-487 (Apr. 1975) and also in other publications. In the space gradient method the amount of movement of each point is computed by the following basic formula: EQU .alpha.=.SIGMA..sub.B d.multidot.sign(g'x)/.SIGMA..sub.B .vertline.g'.sub.x .vertline. EQU .beta.=.SIGMA..sub.B d.multidot.sign(g'y)/.SIGMA..sub.B .vertline.g'.sub.y .vertline.
where ".alpha." and ".beta." represent the movement amounts in the x and y directions, respectively; "d" represents the concentration difference among time-sequential images of one given point, namely, the time gradient; and "g'.sub.x " and "g'.sub.y " represent the space gradients in the x and y directions, respectively, when the image is expressed as "g". And ".SIGMA..sub.B " represents the computed grand total in a block and "sign( )" is the function which outputs the signal of "g'.sub.x " and "g'.sub.y ".
In conventional examples, the detection range has no limits if the spacial concentration distribution of the input images is liner, that is, if the space gradient of the image concentration is constant. In practice, however, the spacial concentration distribution of an image varies in random cycles, therefore, the conventional method has the disadvantage of not being easily applicable to large movements.